Honestly,
I would let my ears, hands, and playing make the decision. Which pedal is most useful for you. Which gives you tones that you find essential for your playing. Which feels better, sounds better, etc.?

Tough call! Against any other OD I've tried, either one would win out handily as a keeper. I use them for different things: the KOT (both sides set to clean) to add flavor to my clean tones, the Klon to goose my overdrive channel. I feel both are indispensable, but forced to choose, I'd probably keep the KOT.

Honestly,
I would let my ears, hands, and playing make the decision. Which pedal is most useful for you. Which gives you tones that you find essential for your playing. Which feels better, sounds better, etc.?

I have both...LOVE the Klon and I like the KOT. I will sell the KOT inevitably, where the KLON will never leave me. It's a really fire breather with my Twin, just too amazing to let go, it will make any amp growl. It just fills everything out and makes the dynamics and response sound SOOOO amazing!

Mr.Klon has been great- I call it the "Butter Box" as it adds fat/warm nuance and boost to any guitar. Very unique all around from its tone to its cast chassis.
I'd love to cascade 2 klons but the heft $$$ of doing that stings while gas is $4+ per gallon

Depends what your after and what amps and guitars you are sing. My Clubman gets very thick sounding as you turn it up so the thickening the Klon offers up might not be a good thing fo rme. I have a KOT right now and use this a my low gainer for everything, it's just th emost musical and real amp tone I have yet to use in a pedal form. The Klon is good but I personally think the KOT has more variability.

Apples and oranges for me. The KLON I use if I can push the amp to it's sweet spot first and then add it to do it's job, OD and heft.
The KoT I use to push a sweet spot into the amp, then use the second stage to OD or boost for solos.
For me, even though they are both OD's, they are not interchangeable. The Kot would be my first choice, but I wouldn't want to not have a KLON.